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Liquid Organic Hydrogen Carriers: Surface Science Studies of Carbazole Derivatives
Author(s) -
Papp Christian,
Wasserscheid Peter,
Libuda Jörg,
Steinrück HansPeter
Publication year - 2014
Publication title -
the chemical record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.61
H-Index - 78
eISSN - 1528-0691
pISSN - 1527-8999
DOI - 10.1002/tcr.201402014
Subject(s) - dehydrogenation , carbazole , reactivity (psychology) , chemistry , photochemistry , platinum , x ray photoelectron spectroscopy , desorption , spectroscopy , hydrogen , platinum nanoparticles , infrared spectroscopy , alkylation , nanoparticle , catalysis , adsorption , materials science , organic chemistry , chemical engineering , nanotechnology , medicine , physics , alternative medicine , pathology , quantum mechanics , engineering
We review recent results towards a molecular understanding of the adsorption and dehydrogenation of carbazole‐derived liquid organic hydrogen carriers on platinum and palladium single crystals and on Al 2 O 3 ‐supported Pt and Pd nanoparticles. By combining synchrotron‐based high‐resolution X ‐ray photoelectron spectroscopy, infrared reflection‐absorption spectroscopy, advanced molecular beam methods and temperature‐programmed desorption spectroscopy, detailed insights into the reaction mechanism are obtained. On Pt (111), dehydrogenation of perhydro‐ N ‐ethylcarbazole, H 12 ‐NEC , starts with activation of the hydrogen atoms at the pyrrole unit, yielding H 8 ‐NEC as the first stable reaction intermediate at ∼340 K , followed by further dehydrogenation to NEC at ∼380 K . Above 390 K , dealkylation starts, yielding carbazole as an undesired byproduct. On small supported Pt particles, the dealkylation sets in at lower temperatures, due to the higher reactivity of low‐coordinated sites, while on larger particles with (111) facets a reactivity as on the flat surface is observed. Carbazole derivatives with ethyl, propyl and butyl chains show an overall very similar reactivity, both on Pt (111) and on Pt nanoparticles. When comparing the dealkylation behavior of H 12 ‐NEC on Pt (111) and Pt nanoparticles to that on Pd (111) and Pd nanoparticles, we find a higher reactivity for the Pd systems.